/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.contrib.streaming.state.iterator;

import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.contrib.streaming.state.RocksDBKeySerializationUtils;
import org.apache.flink.contrib.streaming.state.RocksIteratorWrapper;
import org.apache.flink.core.memory.DataInputDeserializer;

import javax.annotation.Nonnull;

import java.io.IOException;

/**
 * Base class for iterators over RocksDB column families.
 * @param <K> the type of the iterated objects, which are keys in RocksDB.
 */
@Internal
public abstract class AbstractRocksStateKeysIterator<K> implements AutoCloseable {

	@Nonnull
	protected final RocksIteratorWrapper iterator;

	@Nonnull
	protected final String state;

	@Nonnull
	protected final TypeSerializer<K> keySerializer;

	protected final boolean ambiguousKeyPossible;

	protected final int keyGroupPrefixBytes;

	protected final DataInputDeserializer byteArrayDataInputView;

	public AbstractRocksStateKeysIterator(
		@Nonnull RocksIteratorWrapper iterator,
		@Nonnull String state,
		@Nonnull TypeSerializer<K> keySerializer,
		int keyGroupPrefixBytes,
		boolean ambiguousKeyPossible) {
		this.iterator = iterator;
		this.state = state;
		this.keySerializer = keySerializer;
		this.keyGroupPrefixBytes = keyGroupPrefixBytes;
		this.ambiguousKeyPossible = ambiguousKeyPossible;
		this.byteArrayDataInputView = new DataInputDeserializer();
	}

	protected K deserializeKey(byte[] keyBytes, DataInputDeserializer readView) throws IOException {
		readView.setBuffer(keyBytes, keyGroupPrefixBytes, keyBytes.length - keyGroupPrefixBytes);
		return RocksDBKeySerializationUtils.readKey(
			keySerializer,
			byteArrayDataInputView,
			ambiguousKeyPossible);
	}

	@Override
	public void close() {
		iterator.close();
	}
}
